Modern cars and head units are pretty fancy gadget-wise. But what if your car still has an 8-track? No problem. Just pick up a Raspberry Pi 3 and a seven-inch touchscreen, and use Crankshaft to turn it into an Android Auto setup.
The open source project is based on OpenAuto which, in turn, leverages aasdk. The advantage to Crankshaft is it is a plug-and-play distribution. However, if you prefer, you can build it all yourself from GitHub.
The only limitation we can see stems from the lack of audio input on the Raspberry Pi, though we wonder if a USB sound card would take care of that problem. If you have a spare Pi and a screen hanging around, this is a handy project. A 3D-printed Pi case and some kind of mount for the LCD and you can ditch the 8-track. Not to mention with the Pi under there and all the source code, this should be highly hackable.